Portable electronic devices are today ubiquitous throughout society as illustrated by the fact that, in many developed countries, it is estimated that over 90% of their population over the age of sixteen uses a mobile phone. Whilst technical developments in the rechargeable batteries used to power such devices have meant that over the years such devices have become usable for longer and longer periods, a number of issues still remain. These include (1) the need to recharge the device more frequently as the battery ages and (2) the power demands placed by the operation of modern software which inevitably drains batteries faster. As a consequence, most users today are finding it necessary to recharge their devices more frequently than in the past.
This has in turn led to a technical problem because the current lithium ion batteries used today are slow to recharge when plugged into a conventional electricity ring main, typically taking a period of many hours. This is particularly inconvenient for the traveller as evident by the large number of people often wanting to use wall plugs in airports, cafes, conference centres and the like. It would therefore be useful for the traveller to have a reliable portable battery charger, which could both recharge such batteries safely, and itself be quickly rechargeable. Whilst there are a number of such devices on the market they tend to be very bulky and/or still slow to recharge themselves.
One approach to achieving a faster recharge is to use a charger incorporating a supercapacitor as they are able to both hold significant charge and to charge and discharge quickly. However their stored charge density remains small and it has been estimated that a conventional supercapacitor made from double-wound aluminium foil sheets would need to be the size of a small beverage can and weigh around half a kilogram to charge the average smartphone. This makes it impractical to carry and connect to the device.
It is therefore one object of the present invention to provide a battery charger which can rapidly recharge itself, and subsequently a portable electronic device, and another to provide a device that is light enough and small enough to render it portable.